<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>选择器</title>
    <link href="style01.css" type="text/css" rel="stylesheet">
</head>
<body>
    <p class="p1">this is my web page</p>
    <p class="p2">this is my web page</p>
    <p class="p1 p2">this is my web page</p>
</body>
</html>